Generally, semiconductor devices comprise electronic components, such as transistors, capacitors, or the like, formed on a substrate. One or more metal layers are then formed over the electronic components to provide connections between the electronic components and to provide connections to external devices. The metal layers typically comprise an intermetal dielectric layer in which vias and interconnects are formed, usually with a single- or dual-damascene process.
During the fabrication process, it may be necessary or desirable to perform one or more planarization processes. For example, transistors and other devices may be formed on a substrate such that the topology is not planar. Because of this non-planar topology an intermetal dielectric layer deposited over the transistors and other devices also exhibit a non-planar topology. However, it is desirable to form a subsequent metal layer on a planar surface, and as a result, it is desirable to planarize the intermetal dielectric layer in preparation of forming a metal layer.
One method of planarizing a surface is by chemical mechanical polishing (CMP). Generally, CMP involves placing a wafer in a retainer ring. The retainer ring and the wafer are rotated as pressure is applied to the wafer against a polishing pad. A chemical solution, referred to as a slurry, is deposited onto the surface of the polishing pad to aid in the planarizing.
Optimally, the slurry is applied uniformly over the surface of the polishing pad at a location at which the wafer is to contact the polishing pad. If the slurry is not applied uniformly, the wafer may be polished unevenly across the wafer.
Accordingly, an apparatus for and method of applying a slurry uniformly and efficiently is needed.